The goal of the proposed research is to identify herpes simplex virus type 1 (HSV-1) DNA sequences and gene products which regulate gene expression during productive infection. To accomplish this goal, a heterologous gene whose expression is easily quantifiable, will be inserted into each of three kinetically distinct HSV-1 genes. The heterologous gene is that for chloramphenicol acetyl transferase (CAT) placed under the control of the SV40 early promoter. Three types of recombinant viruses will be generated, containing the CAT gene inserted into the individual viral genes. These will be used to infect cells and the kinetics of CAT expression, as influenced by the DNA environment in which it is placed, will be determined for each recombinant. These experiments will identify specific viral sequences that act in cis on the viral chromosome to regulate gene expression. Other viral functions may contribute to the regulation of a heterologous gene by HSV-1 cis acting sequences. These will be analyzed in transient assays by determining the levels of expression of the CAT gene (again flanked by specific HSV-1 sequences) in response to trans acting products generated either from superinfecting virus, or individually cloned HSV-1 genes. In this way, viral sequences can be identified which influence gene expression in cis, and respond to trans acting functions.